The present invention relates to actuators, which may be used over a limited range or in a continuous direction where the desired result is obtained by varying a gap between a fixed stator pole and the permanent magnet rotatable armature. The proposed actuator can be used as a sector motor for devices that require two or three different positions in either a failsafe or a latching configuration or as in a continuous rotating device, which provides additional rotational energy to that device.
The invention relates to a multi-position or continuously rotating actuator, which includes stationary multi-pole (poles) journaled around a rotatable permanent magnet. Essentially, the design of this actuator includes at least two substantially similar poles positioned around an armature and a third pole. The third pole can either be preset at a specific gap distance for a limited range actuator or set to vary at set armature angles for a continuous rotating device. There is an air gap between each of the poles and the rotatable magnet wherein each air gap is set at a distance to produce the desired drive characteristics. Where this device relies on the principle that any freely rotatable magnet will seek or try to seek a position of maximum flux. Thus, with this design, the rotation characteristics of the armature within the housing are dependent upon the differential size of the air gaps between the poles and the armature.
With the design of the limited range multi-position actuator, there are a series of suitable mechanical stops that will limit the operating range to less than 180 degrees. The third pole can be adjusted to create either a failsafe mechanism or a latching mechanism. For the failsafe application, when the third pole is set closer to the armature, the rotatable magnet armature will always seek this mid position when electrical power is removed. Thus, when applying power to either of the first two poles, the armature will rotate to match the poles on the armature to these first two poles. When this power is removed, the magnet rotates back to its mid range fail safe position.
For the latching mechanism, the mid-pole gap is pre-set further away from the armature when compared to the adjacent poles resulting in the armature being stable or latched to either of the two stops since maximum flux occurs at this angle limited by the stops. When powered, this device becomes a simple two position actuator where the latching force is controlled by the gap setting. For a three-position actuator, the mid position will be obtained by using an auxiliary device such as a helper magnet or a spring detent.
For a continuous rotating actuator, the gap distance of the third pole can be varied by using an auxiliary means. Essentially, this gap distance can be made to vary from way out to close in once or twice for each armature cycle for a three-pole device. When timed properly, with the third pole effectively out, forming a large gap, the rotating armature will contribute energy to an attached rotating device by trying to seek a position of maximum flux. When the pole is totally in, forming a tight gap, the armature is effectively balanced and will be in a free wheeling mode. An obvious application for this invention is for a bicycle. If the sprocket hub contains the three-pole device and the rotating sprocket shaft contains the permanent magnet, then a hand linkage could be used to move this third pole in rhythm with the action of the feet pressing on the pedals creating an added energy pulse.
Letting go of this linkage will automatically result in the pole being driven to its tight gap stop. The use of a similar design is shown in U.S. Pat. No. 4,662,644 to Nelson, which is incorporated herein by reference.